1. Field of Invention
This invention relates generally to capotasto devices for uniformly changing the pitch of all strings on a guitar simultaneously. More specifically it acts as a capo for a musical instrument with elevated strings such as a dobro or Hawaiian guitar.
2. Description of Prior Art
Capos are generally known for their application to guitars as an apparatus to uniformly raise the pitch of all the strings by clamping them directly in contact with the fingerboard, thereby engaging the strings onto a desired fret. These types of capos are typically represented by U.S. Pat. No. 390,612 to Moffat (1888), U.S. Pat. No. 1,788,636 to Russell (1927), U.S. Pat. No. 4,143,576 to Nichols (1979), and U.S. Pat. No. 4,583,440 to Myerson (1986). These designs are impractical for use on the typical dobro which has elevated strings, and is not fretted like a guitar, but is played using a solid slide bar. The dobro is generally held in a "flat" position with the neck and strings roughly perpendicular to the player's body. The player brings the slide bar into contact with the strings at a desired place with one hand, using the frets on the fingerboard as a positioning guide while plucking or strumming the strings with the other hand. This differs from a conventional guitar where strings are pressed into contact with frets to determine the pitch of the notes played.
The typical dobro also has some of its strings tuned to a higher pitch than a conventional guitar, thus making the strings more rigid and placing greater stress on the neck of the instrument. This stress is often dealt with by placing a stronger, "square" neck on the instrument, rather than the typical round style neck found on guitars.
A prior art capo for a dobro is represented by U.S. Pat. No. 4,671,156 to Hathcock (1987). This type of device clamps from above and below the strings above the desired fret, "hanging" onto the strings above the fingerboard.
One drawback is the obstruction it places on top of the strings. It is a common practice for the experienced player to hold the slide bar between the thumb, index and middle fingers. The thumb is in front of the bar (towards the body of the instrument), the index finger is on top, and the middle finger is behind the bar. The ring and little finger take up additional space behind the bar. These two fingers are often used to damp the strings behind the bar to eliminate string buzzing and overtones. When the structure of the capo extends above the fret being capoed to, it interferes with the player's middle, ring and little finger, as well as the slide bar, thus crowding and inhibiting movement.
Another unwanted effect occurs when the strings behind the capo (between the capo and the nut), begin to vibrate, creating undesirable overtones. The strings behind the capo vibrate during play, without being touched directly, by picking up the sound produced by the instrument through the air, the neck, the strings, and the capo itself.
A third problem occurs when one or more of the strings, for whatever reason, goes out of tune while the capo is attached. The capo clamps on tightly enough so that the strings do not react predictably when being adjusted by a tuning machine with the capo on. After adjusting a string or strings, they tend to continue stretching or contracting out of tune, while being played as they "settle in", under the pressure of the capo. This often creates a situation of tuning and retuning without satisfactory results. A player may then find it necessary to remove the capo, retune the instrument, and then reattach the capo, resulting in considerable time being wasted.
Another problem with the tight clamping effect of these types of capos is that if they are not clamped to the desired position accurately, they must be unclamped, repositioned, and then reclamped. The tight clamping forces prevent moving them easily (by sliding), to make slight adjustments in accurately setting the pitch. These types of capos also pinch the strings directly against a hard surface, flattening the windings, and otherwise damaging the strings.
There is also a muffling of the tonal quality from the suspended nature of the capo. The nut of an instrument helps in transferring the sound from the strings to the neck and on to the body of the instrument. This cannot be accomplished with a suspended type of capo. These capoes also move vertically, while the instrument is being played, since they "hang" from the strings and are not supported by the neck. The string bounce that this allows is undesirable to the player.
Another prior art is shown in U.S. Pat. No. 3,933,077 to Dunlop (1976). This device has a spacer member under the strings, with a pressure member above the strings that engages the strings to the spacer member by means of an elastic strap. The spacer member may have grooves to accommodate the strings.
As previously mentioned, dobro fingerboards have frets for the player to use as guides for positioning the slide bar. Dunlop does not show these frets in the drawing where his device is being used as a capo for Hawaiian type guitars. These instruments do have frets, however, and as his other drawing shows, the device must be positioned to one side of a fret due to the design of the spacer member. This makes it fundamentally impossible for the capo to retune the instrument accurately in relation to the desired fret. In addition, it renders all of the other frets out of true position since the capo cannot be accurately aligned with its own fret. The various forms of the spacer member may also set the strings back even further from the fret being capoed to. The higher the elevation of the strings above the fingerboard, the larger the diameter of the spacer required, resulting in greater offsets from the capoed fret and producing a larger error in pitch. In addition, the string grooves in the spacer may not match the string spacing on the player's instrument, creating a situation where the player is readjusting to this spacing which can vary when the capo is attached and removed.
Another problem lies in the short leg of the U-shaped member. This object interferes with the players bar hand as it slants above the strings to connect to the pressure member. The bar hand is also cramped by the pressure member which is in very close proximity to the spacer member.
A further problem also occurs with the spacer member. The spacer is designed to slide under the strings across the fingerboard of a dobro type of guitar. Its cylindrical shape has a narrow surface which contacts the fingerboard, a sharp leading edge, and grooves for strings. Repeated sliding and pressing of these surfaces against the fingerboard will cause damage to the surface of the fingerboard.
As such, there is a need for a dobro capo which imitates the nut of the instrument in tonal quality but does not hamper the players bar hand movements, does not muffle the strings, allow undesirable overtones, place more than acceptable wear and tear on the instrument or its strings, and is easily attached and adjusted during play.